1. Field of the Invention
The present invention relates to a method and system for passivating a processing chamber having internal members fabricated from stainless steel and, more particularly, to a method and system for passivating stainless steel members by exposing the members to an acid source, such as citric acid or nitric acid, at a pressure greater than atmospheric pressure, or a temperature greater than 20 degrees centigrade, or both.
2. Description of Related Art
During the fabrication of semiconductor devices for integrated circuits (ICs), a critical processing requirement for processing semiconductor devices is cleanliness. The processing of semiconductor devices includes vacuum processing, such as etch and deposition processes whereby material is removed from or added to a substrate surface, as well as atmospheric processing, such as wet cleaning whereby contaminants or residue accumulated during processing are removed. For example, the removal of residue, such as photoresist (serving as a light-sensitive mask for etching), post-etch residue, and post-ash residue subsequent to the etching of features, such as trenches or vias, can utilize plasma ashing with an oxygen plasma followed by wet cleaning.
Other critical processing requirements for the processing of semiconductor devices include substrate throughput and reliability. Production processing of semiconductor devices in a semiconductor fabrication facility requires a large capital outlay for processing equipment. In order to recover these expenses and generate sufficient income from the fabrication facility, the processing equipment requires a specific substrate throughput and a reliable process in order to ensure the achievement of this throughput.
Until recently, plasma ashing and wet cleaning were found to be sufficient for removing residue and contaminants accumulated during semiconductor processing. However, recent advancements for ICs include a reduction in the critical dimension for etched features below a feature dimension acceptable for wet cleaning, such as a feature dimension below 45 to 65 nanometers, as well as the introduction of new materials, such as low dielectric constant (low-k) materials, which are susceptible to damage during plasma ashing.
Therefore, at present, interest has developed for the replacement of plasma ashing and wet cleaning. One interest includes the development of dry cleaning systems utilizing a supercritical fluid as a carrier for a solvent, or other residue removing composition. Post-etch and post-ash cleaning are examples of such systems. Other interests include other processes and applications that can benefit from the properties of supercritical fluids or high pressure fluids, particularly of substrates having features with a dimension of 65 nm, or 45 nm, or smaller. Such processes and applications may include restoring low dielectric films after etching, sealing porous films, drying of applied films, depositing materials, as well as other processes and applications. However, high pressure processing systems utilizing supercritical fluids and high pressure fluids must meet cleanliness requirements imposed by the semiconductor processing community. Additionally, high pressure processing systems must meet throughput requirements, as well as reliability requirements.
In order to meet the cleanliness requirements imposed by the semiconductor manufacturing community, processing systems utilized for substrate cleaning are fabricated from stainless steel, and they are subsequently passivated by exposing the stainless steel to citric acid, nitric acid, or a mixture thereof. The processing system is exposed to the acid source at atmospheric conditions for a period of time; however, the processing systems still suffer from lack of cleanliness issues, such as metal contamination.